1. Field of the Invention
The present invention relates to an oil and fat composition which, when used in daily life similarly to ordinary fats, can lower the blood cholesterol level of a person having a high cholesterol level. It further relates to a food and a pharmaceutical preparation each containing the oil and fat composition.
2. Discussion of the Background
There are many drugs and food materials which lower the blood cholesterol level and are highly effective in prophylaxis and therapy. However, since these substances are used in the form of a medicine or auxiliary nutrient food, they should be ingested while paying attention to control of the blood cholesterol level of the subject ingesting them.
Among the components effective in lowering blood cholesterol are phytosterols. Phytosterols are contained in plant seeds in large amounts and are contained in ordinary edible vegetable oils in amounts of about 0.1 to 1.0% by weight. Many investigations have been made on the blood cholesterol lowering effect of phytosterols. It has been reported that the daily phytosterol ingestion necessary for significantly lowering the blood cholesterol level is 236 mg to 18 g per day (e.g., Ann. Nutr. Metab., 39, 291, 1995).
For heightening the blood cholesterol lowering effect of a phytosterol, it is effective to dissolve the phytosterol in a fat, such as an edible oil. When the phytosterol dissolved in a fat is ingested, it effectively functions to form micelles in the small intestine competitively with cholesterol and, as a result, the absorption of cholesterol is inhibited.
With respect to foods containing a fat and a phytosterol, "Fat Food Lowering Blood Cholesterol" (L C Liebens; WO 96/38047), for example, discloses a food comprising a natural fat containing tocotrienol and a phytosterol and/or oryzanol; "Process for Producing Edible Fat Composition" (L J Janduck; JP-B 57-26732) discloses an edible oil containing a phytosterol dissolved therein, with the aid of a free fatty acid as a solubilizing agent, in an amount sufficient for imparting a significant cholesterol lowering activity; and "Edible Fat" (Kobayashi et al.; JP-A 57-206336) discloses an edible liquid fat containing vitamin E and a phytosterol in large amounts. Furthermore, "Substance for Lowering High Cholesterol Level in Blood Serum and Process for Preparing the Substance" (Miettinen et al.; JP-A 6-506909) discloses the use of a .beta.-sitostanol/fatty acid ester.